Currently, the images generated in circular-scan displays disposed in cockpits make it possible to display an image decomposed into a plurality of substantially conical parts defined by a distance from a point and an angle. Typically, an image is decomposed into a certain number of angular sectors between two angles THETAn and THETAn+1, the sectors being displayed successively. In each angular sector a ring is defined between two radii Rp and Rp+1. The remainder of the description will refer to the ring Cnp.
The ring Cnp therefore comprises a part of the image displayed and refreshed each time that the scan of the display reaches the angle THETAn.
The problem therefore arises of plotting the image in the portion of images which is contained in the ring Cnp.
Today, the computers customarily used comprise a certain performance capability and make it possible to carry out an image plot of a precision that is given on the basis of a defined size of image which must be displayed.
Generally, a choice of configuration of the computer must be made according to the ratio of the performance of the computer to the precision of the plot or else the size of the image.
FIG. 1 represents a conventional display of an image generated by circular scanning. Generally, notably in aeronautical applications, the image generated comprises 512 circular slices and 512 angular sectors 3 which are not all represented in FIG. 1.
The image generated can comprise colour levels, for example relating to a danger level in the case of a TAWS application or relating to environmental conditions in the case of an application of a WXR radar.
The total image is displayed over a radius R and over an angular portion A. The image is therefore composed of a plurality of rings 2. The position of each ring may be tagged by a double index n p, designating a radius and an angle included in the angular portion.
One of the major problems of display by way of a linear or circular scan of a conical image is the availability of the necessary computational resource.
In the existing devices the plotting of an image is carried out essentially by a function which determines which pixels are the ones which belong to the ring. This analysis is expensive in terms of computation time since it carries out a pixel-by-pixel analysis.
In the case of a TAWS application, each ring comprises a colour representing a relative danger level in proximity to the relief.
A problem with the generation of the images according to the prior art techniques is that according to the size of the ring, the computational power required to generate a conical image on the basis of the radar image transmitted in the form of a rectangular matrix is expensive and does not adapt to the size of the ring. Outside according to the size of the ring which may be less than a pixel, of the order of a pixel or larger than a pixel, the mode of computation of the plot of the image remains the same. No adaptation of the plot of the image according to the size of the rings to be displayed exists.